Implement health modification on enemy kill; add HealOnKillModifier and update death behavior

Assets/Scripts/Systems/EnemyDeathBehavior.cs

@@ -1,3 +1,4 @@
+using System;
 using Interfaces;
 using Sirenix.Serialization;
 using UnityEngine;
@@ -6,13 +7,18 @@ namespace Systems
 {
     public class EnemyDeathBehavior : MonoBehaviour, IDeathBehavior
     {
+        public static event Action<GameObject, GameObject> OnAnyEnemyKilled;
+        
         [OdinSerialize, SerializeField] private int expReward = 5;
         [OdinSerialize, SerializeField] private int coinReward = 1;
         
-        public void Die()
+        public void Die(GameObject killer = null)
         {
             GameManager.Instance.Player.attributes.ModifyExperience(expReward);
             GameManager.Instance.AddCoins(coinReward);
+            
+            OnAnyEnemyKilled?.Invoke(killer ?? GameManager.Instance.Player.gameObject, gameObject);
+            
             Destroy(gameObject);
             
             // later let's add particle effects, sound effects, etc.